March 5, 2015

expert reaction to case of post-exposure vaccination with the VSV-EBOV experimental Ebola vaccine, following needle-stick injury of US medic

A paper published in the Journal of the American Medical Association examined the effects of the experimental Ebola vaccine VSVΔG-ZEBOV, given to a health-care worker who experienced a needle stick while treating patients in Sierra Leone. The researchers report that the physician did not develop Ebola and showed Ebola-specific immune responses, but warn that questions about safety and efficacy of the vaccine cannot be answered from a single case.

Prof. Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“This isn’t the first time that one of the ebolavirus candidate vaccines has been used to try to prevent infection following accidental exposure.

“Even though the person didn’t get infected, we can’t be sure if it was the effect of the vaccine or that the exposure wasn’t sufficient to cause an infection in the first place. You could only work out if the vaccine is useful if you had comparative data for a larger number of people who had similar exposure, and some did and others did not receive a vaccine.  Comparing the proportion that eventually develops infection would give you an idea if the vaccine worked.

“Whether or not such ‘post-exposure prophylaxis’ should be offered routinely is difficult to say, especially when we don’t yet know if the vaccine works. Sure, the vaccine elicited a strong immune response, but we have no idea if this can protect against infection. This is the key issue that we need to find out.”

Prof. Sanjeev Krishna, Professor of Molecular Parasitology and Medicine, St George’s, University of London, said:

“The compassionate use of a VSVΔG-ZEBOV vaccine in a case exposed to Ebola allowed very detailed monitoring of the effects of this vaccine on immune responses and its side effects. Fortunately, this volunteer physician did not develop Ebola. These types of reports (of which this is the second) can complement results from studies in much larger numbers of volunteers being generated by investigators based in European and African countries. These Phase I studies are assessing the safety of the VSVΔG-ZEBOV vaccine and how it can produce immune responses against Ebola protein. Information from volunteers who have received this vaccine in African countries will be of particular interest in light of the announcement that Phase III studies will begin in Guinea this week. These planned phase III studies are the culmination of intense activities by an international group of scientists, funding bodies, industry, governments and the WHO to deliver solutions to one of the most challenging outbreaks of disease in recent history.”

‘Emergency postexposure vaccination with vesicular stomatitis virus–vectored Ebola vaccine after needlestick’ by Lilin Lai et al. published in JAMA on Thursday 5 March 2015. 

All our previous output on this subject can be seen at this weblink:

http://www.sciencemediacentre.org/ebola-outbreak/

Declared interests

Prof. Sanjeev Krishna: “I am involved in a consortium carrying out Phase I studies on VSVΔG-ZEBOV vaccine and funded through WHO by the Wellcome Trust and other agencies.”